package com.chd.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.chd.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {
    private final StringRedisTemplate stringRedisTemplate;

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    @Resource
    private CountingBloomFilter countingBloomFilter;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R, ID> R queryWithPassThrough(String keyPrefix,
                                          ID id,
                                          Class<R> type,
                                          Function<ID, R> dbFallBack,
                                          Long time,
                                          TimeUnit unit) {
        String key = keyPrefix + id;

        // 0. 计数布隆过滤器查询
        if (!countingBloomFilter.mightContain(key)) {
            return null;
        }
        // 1. 从Redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2. 判断是否存在
        if (StrUtil.isNotBlank(json)) {
            // 3. 存在, 直接返回
            return JSONUtil.toBean(json, type);
        }
        // 4. 不存在, 根据 ID 查询数据库
        R r = dbFallBack.apply(id);

        // 5. 不存在, 返回错误
        if (r == null) {
            return null;
        }
        // 6. 存在, 写入 Redis
        this.set(key,
                r,
                time,
                unit);
        // 7. 返回
        return r;
    }

    public <R, ID> R queryWithLogicalExpire(String keyPrefix,
                                        ID id,
                                        Class<R> type,
                                        Function<ID, R> dbFallBack,
                                        Long time,
                                        TimeUnit unit) {
        String key = keyPrefix + id;

        // 0. 计数布隆过滤器查询
        if (!countingBloomFilter.mightContain(key)) {
            log.debug("被计数布隆过滤器拦截");
            return null;
        }
        log.debug("计数布隆过滤器放行");
        // 1. 从Redis中查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        
        // 2. 判断是否存在
        if (StrUtil.isBlank(json)) {
            // 3. 存在, 直接返回
            R r1 = dbFallBack.apply(id);
            this.setWithLogicalExpire(key, r1, time, unit);
            return r1;
            // 热点Key逻辑: 预存, 逻辑过期不可能不存在, 不存在直接返回 null 报错
            // return null
        }

        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();

        if (expireTime != null && expireTime.isAfter(LocalDateTime.now())) {
            return r;
        }

        String lockKey = LOCK_SHOP_KEY + id;
        try {
            while (!tryLock(lockKey)) {
                Thread.sleep(50);
            };
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                R r1 = dbFallBack.apply(id);
                this.setWithLogicalExpire(key, r1, time, unit);
            });

        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            unlock(lockKey);
        }

        return r;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

}
